Biologi - Biology Chapter 6

6

MICRO-ORGANISMS AND DISEASES

What we have learned earlier Micro organisms cause contagious diseases. Tooth decay is caused by the lactic acid produced by bacteria living on the food remnants. Some micro-organisms, toxic substances, alcohol etc cause diseases which affect the liver. Certain diseases affect the respiratory system. They can be controlled and cured. The infection of micro-organism is a cause for diseases in joints.

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BIOLOGY

There are several diseases which affect man. Some of them are transmissible and

Type of

Shape

Diseases

bacteria

others are not. The transmissible diseases are

pneumonia

called contagious diseases. Louis Pasteur discovered that the contagious diseases are caused by the entry of micro-organisms from

Coccus

eye cysts

the surrounding into the body. This discovery helped a lot in the understanding of diseases,

throat infection

to improve methods of treatment and to control the diseases effectively. The tuberculosis

discovery of antibiotics also led to a greater advancement in the modalities of treatment. Bacillus

tetanus

Do you know how pathogens enter the body and how the body reacts to them? It will be quite useful to know about some of

typhoid

the disease causing organisms or pathogens, the disease caused by them and the preventive measures against them.

Bacteria

siphilis Spirillum

The bacteria are of different types.

cholera

Observe table 6a. Understand the shape of different types of bacteria and the diseases caused by them.

Table 6.a Certain types of bacteria and the diseases caused by them

z

How does each type differ in its shape?

z

Have you seen diversity in the shape of

move through liquid medium using certain

similar types?

hairy appendages. Others have slimy outer

You know that we cannot see bacteria

covering which gives them protection.

with our naked eye. Let us examine their other characteristics. Some bacteria can

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Don't you know that the bacteria reproduce by binary fission.

MICRO ORGANISMS AND DISEASES

During favourable conditions it takes

Bacteria which have better

only about twenty minutes for a bacterium to

surviving ability

divide once.

Some halophilic bacteria can live in

If so, how many bacteria will be formed

concentrated salt solution. Some other

from a single one in one day? What will

bacteria can live at a temperature of

happen if conditions are unfavourable?

110oC. They prepare ATP molecules

Observe the figure given below. (6.1.a,6.1.b)

by directly absorbing sunlight but they

How do bacteria overcome the

have no ability for photosynthesis.

unfavourable situations? How does their

Thermoacidophilic bacteria can live at

mode of reproduction differ with respect to

80o C and can survive upto acidic pH2.

the situations? Record the conclusions in

They can be seen in hot springs.

your science diary. Unfavourable situation cytoplasm outer covering

endospores

Figure 6.1.a Endospores are formed from the cytoplasm

Favourable situation

endospore

endospore grows

new bacterias formed and divides

Figure 6.1.b Division of endospores

Temperature is the major factor which

z

affects the multiplication of bacteria. What would be the nature of their multiplication at different temperatures? Analyse the figure

How far does our body temperature help the multiplication of bacteria?

z

What happens to the bacteria and endospores on heating?

6.2.

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BIOLOGY

0

C

boiling point 1000

0

F

2120 bacteria are destroyed when we heat them under this temperatrue for adequate time. More bacteria are destroyed by overheating but not the endosperes.

62.80

1450

400 37.70

1040

body temperature 370

98.60

melting point

1000

36.10

970

150

590

7.20

450

00

320

bacteria slowly increase in numbers bacteria increase in number bacteria increase in number rapidly

bacteria increase in number bacteria increase in number slowly At this temperature the increase in number of bacteria stops, but will not be destroyed.

00

Figure 6.2 Influence of temperature on the multiplication of bacteria

z

When substances are taken out of the

temperature for about fifteen minutes. You

refrigerator, what will happen to the

can imagine why autoclaves are used in

bacteria in them?

hospitals to make the surgical instruments

Record the conclusions in the science

germ free. We get the same result when we

diary.

use the pressure cooker for cooking.

Now you know that endospores can

The micro-organisms like bacteria enter

survive the temperature of even boiling water.

our body, after overcoming several

In order to destroy the endospores they

unfavourable situations. What would happen,

should be heated under high pressure and

once they enter our body?

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MICRO ORGANISMS AND DISEASES

You have seen that our body

understand why this occurs. This is a type

temperature is very suitable for the

of resistance activity . Our body resists

multiplication of bacteria. A lot of waste

against several diseases like this.

materials are deposited in our body as a result of the life processes of these microbes. These are called toxins. Toxins upset the life processes in our body. Sometimes it may destroy the cells too. The temperature of our body raises to make them inactive or to check their multiplication. Rise in body temperature is the first symptom of typhoid. Now you can

Bacteria cause several diseases besides typhoid. Haven't you understood about tuberculosis. This disease is caused by Mycobacterium tuberculosis. Does tuberculosis affect the lungs only? Observe the figure 6.3. Which are the other parts of the body affected by this disease? Prepare notes on that.

central nervous system Eye lymph node

pericardium

adrenal gland kidney

alimentary canal

bone and joints reproductive organs

bone marrow

skin

Figure 6.3 Sites of affection of tuberculosis other than lungs

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BIOLOGY

Disease

Pathogen

Leptospirosis (Rat fever)

Leptospira ictero haemorrhagiae

Vibrio cholerae

Cholera

Tetanus

Clostridium tetani

Mycobacterium leprae

Leprosy

Mode of infection

Symptoms/Other characteristics

Through contaminated food and water, insects like housefly and untidy surroundings

Continuous diarrhoea, vomiting, over tiredness, muscle cramps, dehydration and loss of minerals. If this continues death may occur.

The germs seen in the urine of rat or water may enter into the human body through cuts or wounds on the skin. Through domestic animals, squirrel, rabbit etc. Through continuous contact with the patient

Headache, fever, shivering, body pain, redness of eyes, difficulty to look on sunlight, jaundice. It may affect the organs such as liver, kidney, lungs etc and lead to a severe condition.

From soil, animal excreta, dirty objects, unsterilised instruments. Through wounds

The body will curve like a bow due to sparm and rigidity of muscle. The disease is known as lock jaw because of the difficulty to open mouth. Death may occur due to the constant damage to the central nervous system.

The symptoms may not be seen from 3 to 5 years. Sensation of skin diminishes – rashes will appear, wounds in the fingers and loss of wounded part, swellings appear on the face, saddle nose etc.

Things to be taken care of Dilute rice soup with salt to be given at intervals. Provide medical help at once. Eradication of rats. Take medical help in time.

Seek medical help at the initial stages. By delaying treatment, though the disease can be cured, the bodily deformities still persist. Vaccination should be given

Table 6.b Some diseases caused by bacteria

Do you know the other diseases caused by bacteria? Observe the table 6.b.

Useful Bacteria There are thousands of different strains

Find out more diseases caused by

of bacteria all around the air, in water

bacteria and make a list of them in the

and in soil. Most of the bacteria are

science diary. Bacteria also cause food

useful. They decompose the organic

poisoning.

wastes, produce certain vitamins in the

Bacteria and Food poisoning

body of animals, help in digestion, change milk to curd, ferment grapes to

Bacteria such as Salmonella,

wine, and are used in the preparation

Staphylococcus, Clostridium botulinum

of antibiotics and hormones. Only a

etc poison the food materials.

small group of bacteria is harmful.

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MICRO ORGANISMS AND DISEASES

Vomiting, diarrhoea abdominal pain and headache are the common symptoms

What is their structure? Observe the figure 6.4.

of food poisoning. Bacteria such as salmonella,

nucleic acid

o

staphylococcus etc are destroyed at 55 C.

protein coating

They are infected mainly through meat & other non-vegetarian food items. What are the precautions to be taken against

Figure 6.4 A typical virus

infection from these? Clostridium botulinum is a type of bacteria that grow in tinned meat (tinned

Observe the figure 6.5 and understand the diversity among viruses.

food). It produces a poison, botulin which causes the deadly food poisoning called botulism. This bacteria grow at about 43 o- 47 oC. It is an anaerobic bacteria. The endospores of this cannot be destroyed even by boiling.

Viruses Yo u h a v e r e a l i s e d h o w t h e multiplication of bacteria causes diseases. The viruses are another type of microorganisms and like bacteria they also cause diseases. At present they are a real threat

Figure 6.5 Different types of viruses

to the life of man. Viruses cause a variety of diseases from common cold to AIDS. You have learnt that the viruses show

Try to understand how the viruses

characteristics of life only when they are

multiply after getting entry into a host cell.

inside living cells but shows non-living

(Fig 6.6).

attributes when they are outside.

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BIOLOGY

When the virus particles are formed

Rickettsia Rickettsia are micro-organisms smaller than bacteria and larger than viruses.

in the host cell, the membrane system of the cell gets damaged. Membrane damage

They have close resemblance with

causes rupture of lysosomes and release

bacteria in structure. Rickettsia cause

of lysosomal enzymes. Life processes get

diseases such as Rockie mountain

disrupted and the cell disintegrates. The

spotted

Q-fever.

viruses continue multiplying and cause

Rickettsia are spread through wounds,

damage to more and more cells. This leads

fleas, lice, bugs, food and air.

to a state of disease.

fever,

typhus,

SARS -A New Threat

protein coating nucleic acid

SARS

(Severe

Acute

Respiratory Syndrome) is a severe respiratory disease. It virus stick on to the host cell

was first reported from the south east region mainly from China. The causative organism is considered to be

inject nucleic acids in to the cell

a virus. The disease starts like a flu, then changes to pneumonia

and

severe

respiratory problems which nucleic acids multiplies in the cells

may lead to death. Acute fever, dry cough, respiratory trouble etc are the common symptoms. But sometimes

synthesize protein coating

headache, sprain, diarrohea etc may be found. Infection of this disease is through close

new viruses are formed by joining protein coating and nucleic acids

contact

with

the

patient. Which are the other viral diseases

viruses are coming out by bursting out of the host cell membrane. Figure 6.6 Reproduction of viruses

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besides AIDS? Check the table 6.c and understand more facts about some of them.

MICRO ORGANISMS AND DISEASES

Disease

Causative organism

Mode of infection

Symptoms/Other characteristics

Things to be taken care of

Dengue fever

Dengue viruses

A type of mosquito by the name Aedes aegypti

Sudden and severe fever, severe headache, pain behind the eye balls, loss of appetite, red rashes on the face and chest, nausea. At severe stages there may be sudden fall in the number of blood platelets.

Treatment should start at the initial stages. Severity may cause death. Control of mosquitoes essential

Polio myelitis

Polio virus

Infection through food, water etc.

Fever, headache and weakness of hands and legs. Permanently handicapped due to damage of nerve cells to muscles

Polio drops (oral) should be given in time

Japanese encephalitis

Virus

Through culex mosquito

Severe fever, headache, nausea, vomiting. Difficulty in bending the neck, hallucination, muscle cramps, fainting.

Treatment should be given at the initial stages. Eradication of mosquitoes.

Figure 6.c Some diseases caused by the viruses

Protozoa

Pseudopodia, flagella, cilia etc help

Don't you know about the unicellular organisms called protozoa? Protozoa includes organisms such as amoeba. They differ from the bacteria in having a specific nucleus. Observe picture 6.7 and study the characteristics of protozoa. Prepare

protozoa in locomotion. You know how amoeba reproduces. The protozoa also multiplies through binary fission. How do they overcome the unfavourable situations?

notes in the science diary. nucleus pseudopodia

cilia

nucleus

flagella

nueleus Figure 6.7

Different types of Protozoa 107

BIOLOGY

Pathogenic Protozoa (Disease causing protozoa)

z

Severe fever

z

Chilling and shivering

Some protozoa cause diseases just like bacteria and virus. Dysentery, malarial fever etc are such diseases caused by protozoa.

z

Severe headache

z

Feeling of intense heat in the body

z

Symptoms repeat intermittently

Dysentery Dysentery is a disease caused by infection of small intestine. What are its symptoms?

Disease may gradually affect organs such as the brain and the kidneys, and become fatal. Therefore if fever with shivering develops, blood testing should be conducted to confirm whether it is malaria or not. The

z

Stomach ache

treatment should be taken for the period as

z

Frequent bowel movement

per the doctor’s advice.

z

Blood and mucous in stool

Black water fever

The causative organism is Entamoeba histolytica. How do the infective form of the germs that come out along with the faeces of the patient infect others?

Four different types of plasmodium such

Dysentery causes dehydration and loss of minerals. If no treatment is given in time it may affect the functioning of kidneys and sometimes it may lead to death. Do not stop the treatment even if the symptoms disappear. Complete eradication of the cysts of pathogens can be made possible only through long term treatment. Bacteria also cause dysentery.

pathogens grow and divide in our red

Malaria Malaria spreads through the bite of Anopheles mosquitoes. The causative organism is the protozoan, Plasmodium. What are the symptoms of Malaria? 108

as Plasmodium vivax, Plasmodium malariae, Plasmodium falciparum and Plasmodium ovale cause malaria. Among these the malaria affected by P.falsiparum is the most dangerous. The blood cells and destroy them. The haemoglobin and bile pigments formed due to the destruction of red blood cells are excreted through urine. This makes the urine appear dark in colour. This acute stage called black water fever is associated with P.falciparum malaria.

Fungi Have you noticed black spots on the wet clothes. It is due to a type of fungus. Mould on the bread is also due to fungus. Observe the fungus affected portion of the bread through a microscope. Compare your

MICRO ORGANISMS AND DISEASES

observations with the figure given below.

Infection through body fluids

(6.8) Make notes on it and record it in the science diary.

Diseases may develop even when the body fluids of patient or carriers happen to

spores

mix with that of normal ones.

hyphae

Do you know how the body fluids mix?

Figure 6.8 mould on bread

The body of the fungi called mycelium is made up of long thread like structures

z

through blood transfusions

z

using unsterilised needles and syringes

z

through sexual contacts Sexual diseases are transmitted only

through sexual contacts with the infected person. Gonorrhoea, syphilis etc are examples of sexually transmitted diseases.

called hyphae. You have learnt that the fungus reproduces by spores.

Haven't you heard about the disease called AIDS (Acquired Immuno Deficiency

Afflotoxin is dangerous

Syndrome). The causative organism for this

Afflotoxin produced by the fungus

is the HIV (Human Immuno Deficiency

Aspergillus flavus is dangerous. If a high

Viruses) which attacks lymphocytes that play

dose of it reaches the body it may cause

a significant role in immunity. This disease is

lung cancer. Sometimes this fungus grows

transmitted through body fluids. This can be

on food grains.

transmitted from mother to foetus.

Are fungi pathogenic?

December 1 - World AIDS Day

Fungi cause several diseases. Have

Every year December 1 is observed as

you noticed white patches in between the

World AIDS day with a view to

fingers of dhobies. This is caused by a

making the people aware of the

fungus. Fungi cause patches on skin,

deadful disease, AIDs.

athletes foot, ringworm desease, corn disease etc. Some fungi cause food poisoning. The toxin produced by them sometimes lead to death.

What happens when human immuno viruses attack lymphocytes? Body

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BIOLOGY

becomes susceptible to any disease. You

extracted from micro-organisms. Some

can imagine the consequences. What are

others are produced through chemical

the precautions that are to be taken to

processes. They destroy or make the

prevent such diseases?

microbes inactive. The examples for some

Now we have understood about some infectious diseases. You know that there are other infectious diseases also. What

antibiotics are given below. z

Penicillin

z

Ampicillin

z

Streptomycin

z

Oriomycin

are the important infectious diseases common in your locality? Make a study and prepare a project report.

Disinfectants and Antiseptics

The discovery of antibiotics helped in

You might have noticed that cleaning

the treatment and cure of contagious

lotions such as phenols are used to clean

diseases such as typhoid, tuberculosis etc.

the floor, table and other equipments in

There are many antibiotics in the market

hospitals, hotels, homes etc. What is its

which are useful against many contagious

purpose?

diseases.

Disinfectants are strong chemicals that

Though antibiotics are useful, some of

can destroy microorganisms. Phenol,

them have side effects also. Observe the

bleaching powder, lysol, formalin etc are

table 6 d.

examples. Antiseptics are the chemicals used to destroy microorganisms in the body surface. It includes ethyl alcohol, boric acid, potassium permanganate. Dettol, savlon etc which can be used as disinfectants and antiseptics in dilute form. Care should be taken to avoid mixing of disinfectants with food and wounds.

Antibiotics Antibiotics are antimicrobial substances which can be used internally as well as externally. Some of them are Figure 6.d Antibiotics and their side effects

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MICRO ORGANISMS AND DISEASES

An incidental discovery

lysozyme in tears

In 1928, a Scottish bacteriologist by name

mucus in nostrils

Alexander Flemming was working in St.Mary’s Hospital in London. He cultured bacteria in an agar medium. Once he came to notice that some of the bacteria got

lysozyme in saliva mucus and cilia in trachea

destroyed due to some reaction. By careful observation it was found that a chemical

skin - outer covering

produced by a fungus Pencillium notatum was responsible for the destruction of bacteria. That chemical was pencillin-the first antibiotic. It has the ability to destroy many bacteria. It was first used in 1940. In 1945 Nobel prize for medicine was awarded to Alexander Flemming, H.W Flory and E.B Chain. Don’t you know that

HCl in gastric juice

mucus and enzymes in small intestine bacteria in large intestine

blood clot in wound

lysozyme in urine

lactic acid in vagina

the indiscriminative use of antibiotics is dangerous? Emergence of antibiotic resistant bacteria is a new problem in the

Figure 6.9 Safety measures in the body

field of treatment. z

Do you understand the antibiotics are harmful to us. Production of bacteria which can resists antibiotics is a new

the entry of pathogens into the body? z

You know that diseases occur while pathogens get entry into our body. Though there are millions of pathogens around us, we do not often get an attack of diseases. Why?

How does the body check the pathogens from entering through inspiring air?

problem in the field of medical science.

Safety Measures in the Body

Which is the major safety device to check

z

Where do you see lysozymes which have bacteriocidal property? Make note on different parts of our

body which protect us from the attack of pathogens and give a presentation.

Immune System

Observe the figure 6.9. Find out the

You have now understood the safety

answers to the questions and record it in

measures adopted by the body to prevent

the science diary.

the attack of pathogens? What would be 111

BIOLOGY

the result if this measures fail? The body resists against the disease germs in accordance with their mode of attack.

Notice the changes in affected part of blood vessels. z

What is the use of expansion of gaps on the blood capillaries?

z

Why do the affected parts swell and red coloured?

Have you noticed the appearance of swellings during trauma? Do you know that this also is a method of resistance. Observe the figure 6.10.

Swelling response in the affected area is local and provides immediate resistant

bacteria A

attack of bacteria

activity. You know that a type of white blood corpuscles called lymphocytes

blood capillaries

produce antibodies to resist the disease germs. When more lymphocytes are B

more blood comes out. Blood capillaries dilate. The gap between the walls of the capillareis increases.

needed, the lymph glands in the affected area do extra work to produce more lymphocytes. Such lymph glands also show swelling. That is why wounds are often associated with inflammation of lymph glands.

C

phagocytes coming through the crevices

Immunity You have understood that the human body has an innate power of immunity. Do you know how the body resists the disease germs, once they enter the body. Observe

D

phagocytes engulf the bacteria and destroy them

the Illustration I given below. You have understood why even after the attack of pathogens, we do not always get diseases. Some lymphocytes retain the ability

E

blood capillaries returns to original stage

to produce antibodies even after the body has recovered from the disease. The antibodies once produced will remain

Figure 6.10 Swelling responses in the affected area

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MICRO ORGANISMS AND DISEASES

Antigens All the substances which body considers as foreign bodies Eg: Other protein molecules, Disease germs, Toxins etc.

↓

Quick response

Resistant response

Slow response

General for all antigens (Non-specific)

Phago cytosis

Safety measures in the body-skin, mucus membrane, lysozyme etc.

Special for entering antigens (Specific)

Swelling response

The lymphocytes or antibodies which they produce specifically, destroy or make - the antigens inactive. Illustration I

viable for a long period. You have heard

Health Organisations

that we develop permanent immunity

Have you heard about the World Health

against diseases such as chickenpox,

Organisation? It works with a view to

mumps etc once we happened to be

provide health for all in the world. It

victims of such diseases. Now you may

functions with the guidance of United

knows the reason.

Immunisation Prevention is always better than cure. You have seen that the children are given

Nations. Organisations like UNICEF, International Red Cross, Indian Red Cross Society etc functions in health and social welfare

fields.

There

are

different

organisations working in the national and international level.

April 7 is celebrated

preventive medicines. Do you know what

as World Health Day in remembrance of

are the preventive medicines?

that day in 1948, when all the member countries have signed when the constitution of World Health Organisation.

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BIOLOGY

The killed or inactive disease germs,

to produce antibodies against a specific

inactivated toxins etc are given as

disease. The antibodies once produced

preventive medicines. These are called

will protect the body from the further

vaccines. They act as antigens which

attack germs of that specific disease.

stimulate the immune system of the body The begining of immunisation

The body does not get adequate time to produce antibodies against certain

An English doctor Edward Jenner

diseases such as cholera.

observed that small pox does not

situations, antibodies are directly injected

appear in persons who were once

to attain immunity.

attacked by the disease.

Jenner

injected the pus of small pox with a needle in to a girl from a girl having

In such

Immunisation is a method of giving vaccines inorder to resist the diseases.

the disease. After that the injected

Visit a nearby Primary Health Centre

person showed the symptems of disease

and understand the different vaccines given

and then got cured. After about two

for different diseases.

months he injected the pus of the

immunisation chart and exhibit.

disease from another patient in to the same girl. The girl did not show any symptoms of disease. This experiment in

1796

was

the

begining

of

immunisation. The term vaccination is derived from a Latin word 'vacca' which means cow. The immunisation is also called vaccination in the rememberance of Jenner's small pox injection. The material used for this is called vaccine.

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Prepare an

MICRO ORGANISMS AND DISEASES

SUMMARY ™

There is a suitable environment in our body for the growth and multiplication of the microorganism.

™

Disinfectants, antiseptics, antibodies etc. help to destroy the microorganisms. Majority of antibiotics have side effects.

™

There are special adaptations for microorganisms to overcome the unfavourable situations.

™

™

The microrganism which cause the contagious diseases have different shape and structure.

Our body has a safety measure to prevent the entry of pathogens. When this measure fails, the disease manifests.

™

White blood corpuscles play an important role in destroying the pathogens that enter our body.

™

Through proper immunisation we can prevent many diseases. By taking adequate precautions, the diseases can be checked.

™

Some micro-organisms cause food poisoning.

™

Some diseases are transmitted through air, water, food and by some organisms.

™

Some pathogens are transmitted through body fluids.

FURTHER ACTIVITIES ¬

Explain how the microorganisms cause diseases.

¬

How can we avoid the fungal diseases affecting man?

¬

Some of the diseases which are considered to be under control pose new threats. Eg. Tuberculosis. What explanation would you give for this.

¬

“Carelessness may lead to death”check how far this statement is true in the case of contagious diseases.

¬

Explain the importance of immunisation.

¬

Prepare posters on the importance of cleanliness in controlling contagious diseases.

¬

The immediate treatment to diarrhoea is to control dehydration and loss of minerals. Which are the drinks that can be used for it? Which are the components in the ORS solution and at what proportions? Collect information.

¬

What all things would be planned to observe the December 1 as World AIDS Day? Prepare notes on it.

¬

Collect and Exhibit the pictures in the class of scientists who invented the different antibiotics.

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